Powdered metal valve plate assembly

ABSTRACT

The invention provides a substantially impervious molded sintered iron valve plate arrangement wherein both sides of the valve plate include inwardly relieved surfaces and generally planar outwardly disposed surfaces. The outwardly disposed surfaces are ground flat for properly seating gasketing material thereon. The gasketing material maintains the machined area impervious, while the inwardly disposed surfaces have an outer impervious layer formed by subjecting the valve plate to a steam oxide treatment after its formation from powdered metal.

[ Aug. 7, 1973 United States Patent [191 E y XXXXX 58 0500 16616 ZHBZB ill-1.1. 55555 22.). 3 u "3 .l .l

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[73] Assignee: Westinghouse Electric Corporation,

- Primary ExammerSamuel Scott AttorneyF. H. Henson et al.

Pittsburgh, Pa.

[22] Filed:

Nov. 30, 1971 7 ABSTRACT The invention provides a substantially impervious molded sintered iron valve plate arrangement wherein [21] Appl. No.: 203,299

both sides of the valve plate include inwardly relieved surfaces and generally planar outwardly disposed sur faces. The outwardly disposed surfaces are ground flat for properly seating gasketing material thereon. The

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POWDERED METAL VALVE PLATE ASSEMBLY BACKGROUND OF THE INVENTION 1. Field of The Invention The invention relates to powdered metal articles and, more specifically, relates to sintered iron valve plates usable in compressors or the like.

2. Description of The Prior Art Although the use of powdered metal for the formation of various metallic articles is old and well known, heretofore, its use in the formation of relatively large valve plates efficient at a high pressure ratio has engendered several undesirable characteristics. More specifically, valve plates have been formed by the compacting of, for example, iron powder in a mold or press. The formed plates were then sintered in a controlled atmosphere furnace and then given a steam oxide treatment which hardened the plates and, to a limited-depth, sealed the plates to prevent leakage by filling the pores with oxide particles. Unfortunately, the density of oxide decreased rapidly as one went from the exterior to the interior of the plates.

Thus, subsequent requisite machining of the valve plates in order to provide a smooth surface for the proper seating of gaskets thereon and to provide smooth and flat surfaces for the mounting of intake or discharge valves tended to remove the layer comprising the oxide seal, resulting in the machined surfaces becoming generally porous and thereby providing an area of leakage through the valve plates. Since oxide particle coating of a valve plate could not be obtained having a sufficient depth and uniformity of coating, larger size, powdered metal valve plates were not acceptable for use in compressors or the like having a fairly high dishcarge pressure.

Accordingly, in order to overcome this deficiency and, yet, still utilize the relatively inexpensive sintered iron valve plate, it would be advantageous to overcome the porous nature of such a valve plate so that it would find high utility in high pressure compressors and the like without undesirable leakage of contained gases through it.

SUMMARY OF THE INVENTION The invention comprises a powdered metal valve plate which can be utilized, advantageously, in a compressor or the like with little chance of compressed gas seeping through the valve plate so as to reduce the efficiency of the compressor. In the specific embodiment illustrated, the valve plate comprises a powdered metal (iron powder) (MPIF Spec. No. FN-0208-S less copper) matrix which has been compressed in a mold in a press and formed into a valve plate shape and then sintered in a controlled atmosphere furnace so as to provide a compacted, cohesive member. Upon completion of the sintering operation, the valve plate is given a steam oxide treatment in another furnace and then air quenched. The steam oxide treatment hardens the valve plate and seals the surfaces of the plate to provide a substantially impervious layer by filling the pores adjacent the surfacesof the plate with oxide particles. The amount of iron oxide particles present decreases rapidly as one goes towards the interior of the valve plate.

Since the surface of the valve plate is then in a relatively roughened condition, certain portions of the sur faces must be machined substantially flat for the mounting of gasketing on the valve plate and for the proper mounting of discharge or inlet valves. To prevent removal of the oxide coating from the entire valve plate, the valve plate of the present invention is provided, in the molded state, with depressed areas or inwardly inset surfaces in that portion of the valve plate which do not require flattened surfaces for seating of the gasketing material and/or valve arrangement. The valve plate is then machined in the areas required to be flat for facing engagement the with a gasket raised surface has sufficient thickness in these areas so that the machining, i.e., grinding in the instant case, may be completed without contacting the oxide particle coating occurring in the inwardly disposed impervious areas of the valve plate.

Upon completion, grinding of the valve plate is ready to receive discharge and inlet valves and the requisite gasketing that mounts with the valve plate sealably to a compressor cylinder and head assembly. The gasketing is of such extent and area so as to substantially cover the entire ground surface at least on the cylinder head side of the valve plate except for a limited area where the discharge valve is mounted. The machined surface of the valve plate facing the cylinder side is covered by the inlet valve which maintains this machined surface substantially impervious. Thus, a combination of adjacent abutting surfaces, i.e., gasketing and valves, on the machined surfaces of the valve plate and inwardly disposed unmachined surface is provided to limit the escape of high pressure gases through the valve plate. Then, any leakage that might occur is of such insignificant magnitude so as to not reduce the compressor efficiency to any significant degree.

DRAWING DESCRIPTION For a better understanding of the invention, reference may be had to the preferred embodiment, exemplary of the invention, shown in the accompanying drawings, in which:

FIG. 1 is a plan view of the valve plate taken from the compressor cylinder head side;

FIG. 2 is a cross sectional view of the valve plate taken substantially on line II-II of FIG. 1;

FIG. 3 is a plan view taken in a similar manner as FIG. I, but showing the cylinder head gasket and discharge valve disposed on the valve plate;

FIG. 4 is a plan view of the valve plate taken from the cylinder side;

FIG. 5 is a plan view of the valve plate, intake valve and cylinder gasket taken from the cylinder side; and

FIG. 6 is a cross sectional view taken generally on the line VI--VI of FIG. 3 but showing partially the arrangement of the valve plate in assembled condition with the compressor with which it is used.

DESCRIPTION OF THE PREFERRED EMBODIMENT As is shown most clearly in FIGS. 1 to 6, a valve plate 10 is provided which is formed out of a metal powder such as powdered iron. The process utilized to obtain the valve plate 10 comprises first forming the valve plate 10 by compacting iron powder in a mold in a press. The formed plate is then sintered in a controlled atmosphere furnace and the valve plate 10 then given a steam oxide treatment in another furnace and air quenched. The process of formation of the powdered metal valve plate 10 is considered conventional so no further reference will be given thereto, it being sufficient to state that the steam oxide treatment hardens the valve plate and fills the pores adjacent the surfaes of the with oxide particles to prevent leakage through the plate the. However, it is understood the oxide particles sealing the outer surfaces decrease rapidly in density as one moves toward the interior of the valve plate 10 so that the interior of the valve plate 10 is permeable in nature.

A cylinder head side 12 of valve plate 10 (FIGS. 1 and 3) is provided with a pair of depressed, inset surfaces 14 and 16 which, due to their formation during the molding step of the formation of the valve plate 10, have a coating 18 that is oxide particle impregnated and therefore substantially impermeable and gas tight. The depressed surface 14 is inset relative to a general overall planar outer surface 11 of the cylinder head side 12 of valve plate 10 and is substantially square in configuration, having sides joined together by rounded corners and a taper 19 extending from the surface 11 to the surface 14 so as to provide a smooth transition from the outer surface 11 to the depressed surface 14.

Also depressed inwardly is the recessed surface 16 which is elongated in nature and includes a pair of radiused sides 20 and 22 that lead into and smoothly merge with a pair of short straight sides 24 and 26 and also a side 25. A side 27 completes the configuration of the recessed surface 16. The sides 24, 26, and 27 are each parallel to one of the sides 15 of the recessed surface 14. Rounded corners are also provided for the inset portion 16 so as to provide no abrupt edges to it. Inset portion 16 also include a taper 28 which provides for smooth transition between it and the outer surface 11 of the side 12.

As can be seen most clearly in FlG. 3, the inset surfaces 14 and 16 are located on the cylinder head side 12 of valve plate 10 which is partially covered by a relatively impermeable cylinder head gasket 30. Subadjacent the gasket and encompassing the remaining surface l2 and forming the outer planar surface 11 is a ground surface 32 which has been machined to a flattened condition to accommodate the gasket an the mounting of a discharge valve 34 which will be described in greater detail later. As was indicated previously, the area which forms the surface 32, after machining flat, remains raised relatively to the inset surfaces 14 and 16 so that sufficient molded material must be provided on this portion of side 12 to accommodate flattening of the surface 32 while still maintaining the portions 14 and 16 in an inset, depressed condition relative to the finish ground surface 32 forming the remainder of the side 12. During machining the inset surfaces remain undisturbed and because of their oxide layer remain impervious. Thus, the side 12 of valve plate 10 with the gasket 30 provide a relatively impermeable barrier to the passage of gas therethrough because of the coated condition of the inset portions 14 and 16 and the coverage of the machined area by cylinder head gasket 30. V

Valve plate 10 includes a pair of bores 36, 36 therethrough which form the discharge ports for the valve plate 10. The bores 36, 36 are situated to open in the recessed surface 16 and located substantially centrally relative a center line (not shown) extending through the valve plate 10. These bores form the means for the passage of discharge gases outwardly through the valve plate 10. Valve plate 10 also includes a pair of bores 38, 38 that form the inlet ports for valve plate 10. The bores 38, 38 are located to open in the area of the inset surface 14 adjacent the two inner comers thereof so as to provide a compact relationship between the discharge and inlet ports of the valve 10.

A series of four bores 40, 40, 40 and 40 are also provided adjacent the corners of valve plate 10 to provide a mounting means for the mounting if this valve plate in its final assembly. Bolts (not shown) may conveniently pass through these bores and attach the valve plate 10 to the cylinder casting of the compressor. Valve plate 10 also includes a pair of stepped bores 42, 42, opening at surface 32 which serve as a mounting means for discharge valve 34.

The valve plate 10 includes an obverse side 44 (FIG. 4) that includes an inwardly disposed, recessed or inset surface 46 formed when valve plate 10 was originally processed from powdered iron. Inset surface 46 thereby includes a portion of the coating 18 which is substantially impermeable to the passage of gas therethrough. The inlet ports formed by bores 38, 38 open to the side 44 at the surface 46, with this surface having the general Configuration of a rounded corner rectangle of slightly greater width and length than the area encompassed by the bores 38, 38. The remainder of obverse side 44 is machined flat to provide a flattened surface which is outwardly disposed relative to the inset surface 46 so that no coating 18 is present on this part of the surface of obverse side 44. I

A thin metal plate 48 having a center portion 49 capable of flexing inwardly and outwardly and serving as the reed valve or element for sealing over 38, 38 is disposed against the side 44 of valve plate 10. The thin plate 48 is of substantially the same outer dimensions as the valve plate 10 and extends over nearly the entire flattened surface 50 save for a cutout 51 that separates the main body of thin plate 48 from center portion 49. As will become obvious, since the thin plate 48 is held tightly against the valve plate 10, it serves as a gasketing means (at least in the sense of functioning as a barrier to the passage of gas through a major portion of flattened surface 50), for valve plate 10.

Disposed on the cylinder side of thin plate 48 is a conventional gasket 52 which almost completely covers the thin plate 48 for a cutout 54 providing communication between the center portion of thin plate 48 and a cylinder 56 (FIG. 6) of a compressor 58 with which valve plate 10 is utilized. The gasket 52 thereby providing an opening for the passage of inlet and outlet gases to the cylinder 56.

Referring again now to FIG. 1, it can be seen that the bores 36, 36 each include an extension 60 placing the termination of its bore 36 at the same level as the ground, flattened surface 32. Thus, each of the bores 36 is provided with a smooth and flat ground seating surface for the seating of the discharge valve 34 utilized therewith. It can also be seen in FIG. 4 that the bores 38, 38 are each provided with extension 62 that places the termination of the bores 38, 38 at the same level as machined surface 50 so that the extensions 62 provide a smooth, ground seating surface for the intake valve formed by center portion 49 of thin plate 48.

Turning again now to FIG. 6 wherein the valve plate 10 is illustrated in an assembled relationship with the cylinder 56 with which it is utilized it can be seen that a pair of thin plate type discharge reed valve or elements 64, 64 are mounted over the bores 36, 36. These elements or reeds are spring biased by their own inherent resiliency into a sealing relationship with the termination of the extensions 60, 60. The discharge reeds 64, 64 are limited in their outward movement by means of a valve stop 66, substantially rigid and fixed relative to the valve plate so that movement of the reed valve 64, 64 outwardly causes abutment of them with the valve stop 66. The valve stop 66 and reed valve 64, 64 are assembled to valve plate 10 by means of rivets 68, 68 (only one shown in FIG. 6) that extend through the stepped bores 42 as previously described. The reed valve 64, 64 have substantially the same outline shape as valve stop 66 and, as was noted, seat against ground flattened surface 32 adjacent the rivets 68, 68 so as to be properly mounted relative to valve plate 10.

As is conventional, the cylinder head gasket 30 is mounted with valve plate 10 when the valve plate 10 is in final assembled condition, with the head gasket 30 being disposed between the valve plate 10 and a cylinder head 70 (only partially shown) of the compressor 58 with which the valve plate 10 may be advantageously utilized. Disposed below and seated on the obverse side 44 of valve plate 10 is the thin plate member 48 which permits the entrance of gases to the compressor 64. Disposed below this plate 13 the conventional gasket 52 which seals the compressor cylinder 56 relative to the plate member 48 and valve plate 10.

A cutout 72 on the wall of cylinder 56 of the compressor 58 permits thereed valve 49 to move inwardly relative to the cylinder 56 so that the suction stroke of a piston 74 causes the reed valve 49 to deflect inwardly relative to the cylinder 56. This permits the passage of uncompressed gas into compressor 58. Of course, upon the compression stroke of piston 74, the reed valve 49 moves back to the position illustrated in FIG. 6 and seals over the bores 38 to prevent a flow of compressed gas from flowing outwardly of the compressor at this point. During this same compression stroke of the piston 74, upon the pressure within the cylinder 56 reaching a predetermined value, the inherent resiliency of the reed valve 49 is overcome so that a flow of compressed, pressurized gases passes outwardly of the cylinder 56 through the discharge bores 36, 36.

The flow path for unwanted gas leakage through the valve plate 10 is almost completely prevented by the arrangement described. Since the recessed surfaces and gasket means (including the thin plate 48) substantially overlap relative to one another going from one side to the other of the valve plate 10, nearly all leakage gas must take a tortuous path to escape through the valve plate. Thus, a substantially gas tight sintered metal valve plate assemblage is provided for use with a compressor or the like.

It should now be clear that the invention described provides a powdered metal formed valve plate assemblage which is substantially leak free and which accomplishes, in conjunction with the gasketing means an arrangement whereby an inexpensively manufactured compressor is obtained.

What is claimed is:

l. A substantially impervious sintered metal valve plate and sealing means assembly for preventing the leakage of high pressure gas through said valve plate; said valve plate having opposing generally planar surfaces which include at least first and second areas, said first areas being distinct from said second areas by defining a generally planar machined surface for facing engagement with said sealing means substantially preventing the passage of gas through said first areas; said second areas being depressed from the plane of said first areas and having a gas-impervious surface layer, said second areas including substantially all of said opposing surface not in facing engagement with said sealing means whereby, the assembled plate and sealing means is substantially gas-impervious.

2. Structure according to claim 1 wherein the first areas on one surface of said plate laterally overlap the second areas on the opposite surface of said plate.

3. Structure according to claim 2 wherein said gasimpervious surface layer of said second areas is an oxidized layer.

t l 4 il it! 

1. A substantially impervious sintered metal valve plate and sealing means assembly for preventing the leakage of high pressure gas through said valve plate; said valve plate having opposing generally planar surfaces which include at least first and second areas, said first areas being distinct from said second areas by defining a generally planar machined surface for facing engagement with said sealing means substantially preventing the passage of gas through said first areas; said second areas being depressed from the plane of said first areas and having a gas-impervious surface layer, said second areas including substantially all of said opposing surface not in facing engagement with said sealing means whereby, the assembled plate and sealing means is substantially gas-impervious.
 2. Structure according to claim 1 wherein the first areas on one surface of said plate laterally overlap the second areas on the opposite surface of said plate.
 3. Structure according to claim 2 wherein said gas-impervious surface layer of said second areas is an oxidized layer. 